1. Field of the Invention
The present invention relates to automatic component feeders of the type used in automatic component placement machines. More particularly, the present invention relates to a tape feeder for precisely positioning a sprocketed tape having a cover tape on a carrier tape which covers a recess pocket in the base tape or carrier tape for automatically positioning it in a pick up station of a pick and place machine.
2. Description of the Prior Art
Tape feeders for pick and place machines are classified in U.S. Class 226, Subclasses 62, 122, 128, 129 to 139, et al. Covered tapes for tape feeders have become standardized to the point that reels of tapes with components may be purchased from different component vendors knowing that the covered tapes will fit into most standard tape feeders. Such tapes are made to EIA industrial standards with sprocket holes on 4-mm pitch for 8-mm tapes. Like 35 mm movie film, the sprocket holes are punched in staged die sets and are highly accurate for most purposes and have been found to be more accurate than the tape positioning mechanisms used to position the tape in the pick up station.
Heretofore, tape feeders have employed sprocketed wheels which have been driven by levers, escapement pawls and gears which when activated are dependent upon the accuracy of the drive mechanism. Since all of the prior art positioning devices have free play or backlash, it has been difficult if not impossible to position the sprockets as accurately as the sprocket holes in the tape would permit.
Accordingly, it would be desirable to provide a tape feeder that is capable of accurately positioning the sprocket holes and thus the recess pockets which hold components to an extremely high degree of accuracy when operated at high speeds over long periods of time.
It is a principal object of the present invention to provide a novel tape feeder for advancing component carrier tapes into a workstation or feed station with an extremely reliable degree of positioning accuracy.
It is a principal object of the present invention to provide a novel tape feeder that is interchangeable with existing tape feeders, yet provides a higher degree of positioning accuracy than prior art tape feeders.
It is a principal object of the present invention to provide a novel sprocket drive for a tape carrier that has gross positioning gear drive and a fine positioning cam drive.
It is a principal object of the present invention to provide a highly accurate cam drive for positioning a novel sprocket after introducing backlash in the sprocket gear drive.
It is a principal object of the present invention to provide an optical interrupter sensor for a drive motor for sensing a desired gross position of the novel sprocket drive gear.
It is a principal object of the present invention to provide a continuous tape path that does not reverse direction or tend to delaminate the cover tape from its carrier tape.
It is a principal object of the present invention to provide a novel cover tape removal station that prevents components from escaping until being positioned at the final pick up station position.
It is a principal object of the present invention to provide a two-stage tape positioning mechanism that eliminates high-speed overdrive positioning of the carrier tape.
It is a general object of the present invention to provide an economical and reliable high speed tape feeder with a minimum of wearing parts that could effect the accuracy of positioning of a tape carrier.
It is a principal object of the present invention to position a tape carrier in a pick up station independent of the position achieved by the drive motor.
It is a principal object of the present invention to finally position a carrier tape in a pick up station without using the force of a drive motor.
According to these and other objects of the present invention, there is provided in a tape feeder comprising a base plate and cover plates. A motor driven gear drive is mounted on the base plate and comprises a sprocketed wheel for engaging a sprocketed carrier tape and for gross positioning recess pockets in the carrier tape into a pick up position of a work station comprising an automatic cover tape stripper. The sprocketed wheel is further provided with a positioning cam that cooperates with a mating positioning cam which fine positions the sprocketed wheel after it is gross positioned by the drive motor. In the preferred embodiment of the present invention, an optical sensor controls the drive motor to a gross position and a spring actuated drive cam then cooperates with the positioning cam on the sprocket wheel to effect fine positioning of the sprocketed wheel. The sprocketed wheel and carrier tape is then positioned to the accuracy of the carrier tape of better than xc2x1 one 1,000th of one inch.
FIG. 1 is a right side elevation view of a prior art tape feeder with the right side cover plate removed to show the feed path of the component tape;
FIG. 2 is a left side elevation view of the prior art tape feeder of FIG. 1 with the left side cover plate removed to show the tape drive gearing;
FIG. 3 is a right side elevation view of the present invention""s tape feeder with the right side cover plate removed to show the novel feed path of a component tape and the drive mechanism for the sprocketed wheel;
FIG. 4 is a right side elevation view of the present invention frame or base showing the path of the cover tape after being stripped from the carrier tape;
FIG. 4A is a right side elevation view of another preferred embodiment tape feeder showing a take up reel in place of a stuff box and a pinch roll in a changed position;
FIG. 5 is an exploded view of the drive gears employed to drive the sprocketed wheel to a gross position;
FIG. 6 is an isometric view of the tape feeder with side covers attached looking down on the pick up station as the cover tape is removed from the carrier tape;
FIG. 7 is an isometric view of the tape feeder of FIG. 6 taken from the right side showing access slots in the right side cover plate for positioning the cover tape;
FIG. 8 is an isometric view of a carrier tape showing sprocket holes and component pockets;
FIG. 9 is a cross-section taken through the novel sprocketed wheel;
FIG. 10 is an enlarged left side view of the sprocketed wheel of FIG. 9; and
FIG. 11 is an enlarged partial view of the sprocketed wheel of FIG. 10 showing a spring-loaded positioning actuating cam in a cam recess.